Many battery powered, portable external devices and implantable medical devices are known, such as device 100 illustrated in the schematic circuit diagram of FIG. 1, that incorporate a single battery (or bank of batteries) 102 that provide power to low voltage circuitry 104 and high voltage circuitry 106. The low voltage circuit 104 represents components or devices that require a relatively lower power and lower operating voltage to operate properly than the components or devices represented by the high voltage circuit 106. The low operating voltage is typically lower than the output or terminal voltage VBAT of the battery 102. The components and devices represented by the high voltage circuit 106 typically require a high operating voltage, which is typically greater than the battery voltage VBAT. The high voltage circuit 106 also generally draws a higher current during operations than the low voltage circuit 104.
The high voltage circuit 106 is periodically powered by a high voltage power supply circuit or step-up (boost) voltage converter 108 that draws current from the battery 102 and generates the voltage (VH) demanded by the components or devices of the high voltage circuit 106 to operate properly. The relatively high current draw of the high voltage circuit 106 causes VBAT to drop due to the internal resistance RBAT of the battery 102. This drop in the available battery voltage VBAT can prevent the low voltage circuit from receiving the low operating voltage that is required by the low voltage circuit 104 to operate properly.